The present invention relates to expandable cylindrical devices, and has particular application to expandable mandrels. Such mandrels may be used, for example, to clamp in position two cylindrical members for butt-welding them together.
Many prior expandable mandrel devices have utilized circumferentially segmented apparatus which is characterized by gaps between the segments in the expanded condition. These gaps are disadvantageous, particularly in welding applications.
Segmented expandable mandrels have been provided which afford a substantially continuous cylindrical surface in the expanded condition, but such mandrels have typically been characterized by a large number of segments, each of which must be separately driven, resulting in an expensive and complex construction.
Furthermore, heretofore expandable mandrels of the type utilized for welding applications have been specifically adapted for use with tubular members, such as pipe sections, which remain fixed during the welding operation. Accordingly, these mandrels have not been suitable for use with workpieces which must be rotated during the welding operation.